The present invention relates to a switching device.
It is normal practice for electric tools, especially electric hand tools, to be switched on and off with the help of, for example, tumbler switches, possibly with a rocker-like structure, or sliding switches, these switches being either fixed in a suitable manner on the outside of the housing or so arranged that only their actuating parts project through openings in the housing and can therefore be appropriately operated by the user. In many electric hand implements, drills, hammer drills and the like being cases in point, it is also customary to combine the switching on and off with a speed control by mounting a sliding switch in the manner of a pistol grip, so that a finger can be placed around it; the implement will then be switched on by the initial movement of the switch, while subsequent free displacements of the slide serve--for example--to operate a potentiometer, which could also form part of a phase control circuit, so that the speed of revolution of the motor driving the electric hand tool can be increased until the slide comes up against its stop.
Reversal of the direction of rotation is also a customary feature of numerous electric hand tools, screwdrivers being a case in point, because screws can then be either driven or removed. Normally this is likewise done by simple electric switching of the current supply to the stator and/or the brushes, although this is not an optimal solution as far as the efficiency is concerned, because in the latter case one should really arrange for a mechanical/geometric displacement of the brushes through specified angular amounts. Apart from this external switchgear, it is also known (DE-OS 36 06 926) for the circuitry of electric hand tools to be built up with the help of plug-in components, so that wiring requirements become reduced and a large number of conducting parts, including components for direction reversal and switching on and off, assume the form of conducting links that can be inserted in appropriate plastic parts, including housing parts, and--where appropriate--be incorporated in such parts already during manufacture. In this known electric hand tool in the form of a hand drill (DE-OS 36 06 926), the elements and conductors that make up the electric circuitry are designed in the form of block modules or units that can be plugged into each other.
In connection with electric hand tools it is also generally known (DE-PS 33 11 557) to arrange a bridge-like holding part at one end of the stator for the electric motor of a hand tool, a part that can also be described as a motor bridge. This motor bridge is intended to position and sustain the roller bearing for the rotor shaft that is supported in this manner, and the bridge can be appropriately attached to the stator by arranging on the end face of the bridge a series of pins pointing in the direction of the stator, these pins making it possible for the motor bridge to be pinned into the stator and thus to be correctly aligned. At one and the same time, the motor bridge--with its seating aperture for the associated roller bearing of the rotor shaft--also ensures the final position that determines the air gap.
Now it is the object of the present invention to simplify the electrical switching--including, for example, the switching on and off and direction reversal, of an electric tool, especially an electric hand tool, and to obtain a drastic reduction in the wiring requirements of at least one of the switching processes by intervening directly in the motor's own wiring and/or the control possibilities that already exist in the motor.